A homogeneous computer network Analysis and simulation

A network of minicomputers to support transaction processing against a distributed data base is described. This paper gives a brief overview of the design based on a loop communications subnetwork and then describes analytic and simulation models that have been used to predict performance.Service demands in this network are assumed to have the following characteristics.Transaction: Users at on-line terminals enter messages that invoke short computations, a few accesses to the data base and a response message that is then sent back to the terminal.Locality of reference: Transactions entering at one node in the network can almost always be serviced locally, the fraction requiring remote service is expected to be in the 10% to 30% range.The network has been modelled analytically as a network queues. The predictions of this model have been compared to those of a large simulation of the network in an attempt to validate that simulation model. Agreement is good for a two host network over a broad range of network loading. The simulation program has been used to study a large number of problems where we varied: transaction characteristics, remote traffic fraction, host configuration and communications subnetwork speed. One such experiment is described here in detail.     

Altered rhodopsin regeneration in diabetic mice caused by acid conditions within the rod photoreceptors

BACKGROUND: We sought to describe changes in spirometric variables and lung volume subdivisions in healthy subjects and patients with chronic obstructive pulmonary disease (COPD) during moderate acute hypobaric hypoxia as occurs during air travel. We further questioned whether changes in lung function may associate with reduced maximum ventilation or worsened arterial blood gases. METHODS: Ambulatory patients with COPD and healthy adults comprised the study populations (n = 27). We obtained baseline measurements of spirometry, lung volumes and arterial blood gases from each subject at sea level and repeated measurements during altitude exposure to 8000 ft (2438 m) above sea level in a man-rated hypobaric chamber. RESULTS: Six COPD patients and three healthy subjects had declines in FVC during altitude exposure greater than the 95% confidence interval (CI) for expected within day variability (p < 0.05). Average forced vital capacity (FVC) declined by 0.123 +/- 0.254 L (mean +/- SD; 95% CI = -0.255, -0.020; p < 0.05) for all subjects combined. The magnitude of decline in FVC did not differ between groups (p > 0.05) and correlated with increasing residual volume (r = -0.455; <0.05). Change in maximum voluntary ventilation (MVV) in the COPD patients equaled -1.244 +/- 4.797 L x min(-1) (95% CI = -3.71, 1.22; p = 0.301). Decline in maximum voluntary ventilation (MVV) in the COPD patients correlated with decreased FVC (r = 0.630) and increased RV (r = -0.546; p < 0.05). Changes in spirometric variables for patients and controls did not explain significant variability in the arterial blood gas variables PaO2, PaCO2 or pH at altitude. CONCLUSIONS: We observed a decline in forced vital capacity in some COPD patients and normal subjects greater than expected for within day variability. Spirometric changes correlated with changes in reduced maximum voluntary ventilation in the patients but not with changes in resting arterial blood gases.     

The BAX gene, the promoter of apoptosis, is mutated in genetically unstable cancers of the colorectum, stomach, and endometrium

OBJECTIVE: The study's objective was to determine whether there is a difference in the plasma concentration of adrenomedullin, a hypotensive peptide, between arterial and venous umbilical cord blood of uncomplicated gestations with vaginal delivery. STUDY DESIGN: Arterial and venous umbilical cord blood was obtained immediately after vaginal delivery of 44 term infants with uncomplicated antepartum and intrapartum courses. Radioimmunoassay was performed to assess adrenomedullin concentrations in the plasma. The paired t test was used to compare arterial and venous concentrations. Significance was set at P < .05. RESULTS: Mean +/- SE adrenomedullin concentrations were 178.7 +/- 4.7 pg/mL and 190.6 +/- 6.3 pg/mL for arterial and venous cord plasma, respectively. The difference between the 2 concentrations was not significant (11.8 pg/mL, P = .09). CONCLUSION: Arterial and venous umbilical plasma concentrations of adrenomedullin do not differ significantly in uncomplicated gestations terminating with uncomplicated vaginal deliveries. This suggests that in the normal state there is neither net production nor net clearance of adrenomedullin in the placenta.     

The perioperative morbidity of scheduled cesarean hysterectomy

OBJECTIVE: To compare the outcomes of patients undergoing scheduled cesarean hysterectomy with those of women treated with cesarean delivery and subsequent hysterectomy. METHODS: Through a retrospective review of 43 patients, we investigated the morbidity associated with scheduled cesarean hysterectomy and compared these findings with the combined morbidity of scheduled cesarean delivery and subsequent abdominal hysterectomy in a control population. Controls were included only if the subsequent hysterectomy was performed within 3 years of the index cesarean delivery. Each study subject was assigned two controls matched for age, parity, number of previous cesarean deliveries, and indications for procedures. The incidence of the following major morbidity events was compared between the groups: transfusion, urinary tract injury, fistula formation, cellulitis or endometritis, postoperative abscess or hematoma formation, ileus, pneumonia, and wound complications requiring prolonged therapy (seroma, hematoma, infection). RESULTS: The number of women receiving transfusions after scheduled cesarean hysterectomy was greater than among controls (39.5 versus 15.1%; P < .05). The proportion of patients with major morbidity, exclusive of transfusion, was significantly greater in the control population (44%) than in women with scheduled cesarean hysterectomy (16%) (P < .05). The cumulative number of women with a major complication, such as transfusion or a morbid event, was 22 of 43 in the study group versus 44 of 86 in the control population, a nonsignificant difference. CONCLUSION: We found no significant difference in the cumulative perioperative complication rates in women undergoing scheduled cesarean hysterectomy compared with a population of similar patients treated with cesarean delivery and subsequent abdominal hysterectomy.     

Anophthalmic socket and orbital implants. Role of CT and MR imaging

The role of CT and MR imaging examination of orbital implants and the anophthalmic socket is expanding constantly. As the imaging techniques gain refinement and resolution, the list of potential clinical application grows. Frequent clinical-radiologic queries regarding the anophthalmic socket include neuro-radiologic findings with congenital anophthalmia or bilateral microphthalmia, the vascularization or position of an orbital implant following enucleation, or orbital recurrence of tumor following enucleation. Common clinical-radiologic questions regarding orbital implants relate to the associated findings of trauma, infection, bleeding, or recurrence of tumor in relationship to the existing orbital implant.     

High-dose etoposide enables the collection of peripheral blood stem cells in patients who failed cyclophosphamide-induced mobilization

A case of an intracranial cavernous angioma, which presented with headaches and seizures in a pregnant patient, is described. Diagnosis was established with magnetic resonance imaging. A computer-assisted literature search uncovered no previously reported case of intracranial cavernous angioma initially presenting during pregnancy.     

Radicular compression by brucellar epidural abscess

Fifteen children with protein-energy malnutrition and eight healthy children between the ages of 6 months and 60 months were studied for blood glucose and serum insulin levels in the fasting state and 120 minutes following oral glucose load. The measurements were repeated after normalization of the body weight following 6 weeks of nutritional rehabilitation. The fasting blood glucose increased significantly in the post-treatment period and became comparable to the control value. The abnormal blood glucose response to oral glucose load also normalized. The serum insulin level rose significantly (p < 0.001) in the post-treatment period but failed to normalize. The response to oral glucose load was similar. The observed lower insulin response, despite normoglycemia, after 6 weeks of nutritional rehabilitation indicates persistence of hormonal imbalance which may need a longer duration of rehabilitation for full recovery.     

Interactive panoramic map-like views for 3D mountain navigation

In 3D terrain navigation applications, the views based on general perspective projection often find features of interest (FOIs) being occluded. As an alternative, panorama-like views preserve the similarity between 3D scenes before and after the deformations while ensuring the visibility of interested features. In this paper, an automatic method for generating panoramic map-like views is proposed in mountainous areas. The created panorama-like views by moving up the view position as well as the terrain deformation can successfully avoid occlusions of the FOIs. The final views also ensure the resemblance in appearance for the FOIs and landscapes, and thus satisfy the demand for interactive occlusion-free navigation in 3D complex terrain environments.     

Computing at the high school level: Changing what teachers and students know and believe

Research indicates that students often opt out of computing majors due to a lack of prior experience in computing and a lack of knowledge of field-based job opportunities. In addition, it has been found that students respond positively to new subjects when teachers and counselors are enthusiastic and knowledgeable about the area. The summer program described here is designed to improve high school students, teachers and guidance counselors understanding of the opportunities available in computing related fields, specifically information technology through a summer enrichment experience. The hypothesis of this work is that by exposing teachers and counselors to professional development in this field, their attitudes, beliefs and knowledge regarding information technology will be enhanced, thus impacting students’ attitudes (both attending the program and beyond) with respect to information technology and their desire to pursue degrees in this area. Results indicate that the design of this summer program enhanced the knowledge and interest of high school students with respect to information technology. Teachers’ knowledge was also positively influenced. Further refinements are necessary in the design of this program to improve the experiences of guidance counselors.